Why does the button in the checkout always say “Subscribe now” (even for lifetime packages)?

The slightly lighter background area in the booking process at steps 3 and 4 comes entirely from our payment service provider Paddle (integration is done via a so-called IFRAME):

This means that although we have control over the design up to the frame marked in red above, we have very limited influence within this frame.

E.g. we don't have any influence on the labeling of fields, buttons and other texts.

That is why the main button says “Subscribe now” not only for monthly packages, but also for lifetime and support packages.